The present invention is directed to an apparatus for the controllable removal of one or more phases from a liquid-liquid extractor, having a mixer and a settler for light and heavy phases, useful in the treatment of organic solvent wastes from radioactive systems.
Various systems are known for controlling the removal of one or more phases present in a settler of a liquid-liquid extractor. These systems are generally susceptible to breakdown during their operation and, therefore, require systematic maintenance. Such systems are particularly not suitable for use in processing of radioactive substances wherein it is imperative that the system used is dependable and substantially maintenance free.
The various float or control valves, due to their susceptibility to malfunction, have not found use in controlling the removal of liquids from settlers in radioactive waste processing plants. The removal of the heavy liquid phase from liquid-liquid extractors in such processing plants is generally controlled by pneumatic syphoning systems. The drawback of these syphoning systems is that they tend to clog even when there is only a small amount of solid contaminants present and, further, they cannot be operated dependably in systems employing more than two phases. The removal of a light phase from a settler by an overflow aided by means of incoming air is well known as discussed by Treybal, in Liquid Extraction, page 455, McGraw-Hill (1963) and by S. M. Stoller et al, in Reactor Handbook, Volume II, page 581, Interscience (1961). Such a system, though, is restricted to the removal of only the light phase located at the top of the settler and there is no regulation of the light and heavier phase interface position in the settler.
The object of the present invention is to provide an apparatus for automatically regulating the phase interphase position in relation to the properties of the light and heavier phases contained in the settler and provides a control which is substantially maintenance free. The apparatus of the present invention is particularly useful in the treatment of organic wastes from radioactive processing systems and especially suitable in the phosphorus acid adduct treatment of such wastes.